Miklos Szeredi:> It's always easier to review something with less features, even if> that feature set is too little for real world use.

Generally I agree with you.

> The simplest version is with all branches read-only. That gets rid of> a _huge_ amount of complexity, yet it's still useful in some> situations. It also deals with a lot of the basic infrastucture> needed for stacking.

If you really think it is a better way to get merged into mainline, thenI'll try implement such version.

> And that's when one starts thinking about whether unioning is really> the right solution. Instead this could be implemented with a special> filesystem format that only contains deltas to the data, metatata and> directory tree. It would be much more space efficient, could easily> handle renames, hard links etc, without all the hacks that> unionfs/aufs does.

It sounds like an ODF (on disk format) version of unionfs (while itseems to be inactive).At implementing, I don't think it easier to maintain delta of filedataand metadata. Since aufs has a writable branch in it, it is better andeasier to maintain data in a branch fs.If you think there should not be any writable branch in aufs, and all"write" goes to a new filesystem format, then it is equivalent to awritable branch, isn't it?If you say "just a part of write" goes to a new fs, then I don't thinkwe can support several essential features, for instance mmap.